This post on the official forums details the planned updates for SWTOR running through to August.

Update 2.2 (June 11th)Nothing for me in this update as I’m not really playing my level 50 main and I’m certainly not planning on running Nightmare Mode Operations anytime soon! The extra experience buff based on guild size is a bit meh, why do all game developers seem to hate small guilds!?

Double XP weekends for three weekends (June 22nd to July 7th)Hmm, I actually try and avoid these generally as they can really screw with your questing experience if you actually, you know, enjoy doing content on-level.

Relics of the Gree (July 23rd)
This same event will be back in its level 55 incarnation for two whole weeks. I’m running out of time getting rewards from this first run as there’s only three dailies I can solo without PVP-flagging. Hmm, do I get the expansion and level my sage main character up to 55 in time for late July..?

Update 2.3 (Aug 6th)
This update sounds more promising as it promises a new daily zone, a new recurrent event and rather intriguingly a significant graphics update. Colour me interested as people say on the Interwebz!

N.B All dates relate to MMO content releases, i.e. take them with a massive pinch of salt.